This invention relates to a process for the production of abrasive materials by pouting molten abrasive material into the spaces between an assembly of cooling plates consisting of cooling plates vertically arranged parallel to one another, solidification, removal and size reduction.
Processes for the rapid cooling of molten metal oxides have long been known. Thus, according to German Patent Document DE-A 22 27 642, this is done by pouring the molten material between cooling plates. In addition, German Patent Document DE-C 24 14 036 describes a process for the continuous production of an oxidic abrasive of controlled crystal size, in which a melt of the abrasive is poured off into wedge molds, several wedge molds being joined circularly together in the form of a star wheel to form a casting arrangement. The wedge shape of the molds prevents the solidified material from caking. However, it also causes an unwanted crystal size distribution. The described process is virtually impossible to carry out at constant temperatures because the casting arrangement naturally heats up to an increasing extent in operation.
A fine and homogeneous crystallite structure with a single particle size distribution, which is essential for a high grinding performance, cannot be obtained by the process according to German Patent Document DE-C 24 14 036.
U.S. Pat. No. 3,993,119 describes a process and an arrangement for continuously cooling metal oxides in which the liquid metal oxide is poured off through a casting hole into a narrow gap between vertically arranged cooling plates which are moved past beneath the casting hole in a tube. The plates are then moved slightly apart from one another outside the casting position so that the still hot material can be removed. One disadvantage of this process is that it is extremely difficult with the described arrangement to guarantee a uniform narrow gap between the plates. When the molds are emptied, pieces of material cannot be prevented from becoming wedged between the cooling plates. The gap in question is thus widened so that the cooling conditions are altered with the result that a homogeneous, finely crystalline structure can no longer be obtained. In addition, in the event of continuous operation of the casting arrangement described in U.S. Pat. No. 3,993,119, heating of the cooling plates cannot be avoided despite the cooling system provided. However, the quality of the cast product depends to a large extent on the temperature of the cooling plates, so that uniform quality cannot be guaranteed in the disclosed arrangement.
In addition, German Patent Documents DE-A 2 264 202 describes a process for the production of abrasive materials in which the molten abrasive material is cast between several metal or graphite plates spaced apart from one another and is solidified by cooling. However, uniform production conditions, more particularly the residence time of the abrasive material, are not guaranteed in this arrangement. Moreover, the solidified material is extremely difficult and expensive to remove.
The problem addressed by the present invention was to provide a process which would not have any of the described disadvantages of the prior art.